When I take a longish drive I end up with strange black venting-like marks along the rear doors and the panels. Can't figure out how to get a photo on this but I thought I'd ask anyway. Any ideas what's happening here? What can I do about it?

 

why you are not able to take any photos there. is there any problem

 

I am told by Honda that this is ordinary road grime but the question remains as to why it forms in this particular way--don't see it on other cars. I seems to me that air must be venting thru or around these areas in a way that concentrates the "road grime" there. Poorly sealed or ??? Happens on both sides, always on the rear panels.

 

When's the last time you waxxed your Fit? A good wax job will keep dirt a bay.
Not saying you don't have something else going on 2.